Study on the influence of methyl groups and their location on properties of triphenylamino-based charge transporting hydrazones

Article abstract of DOI:10.1007/s00706-009-0202-y

Methyl substituent effects on the HOMO and LUMO energy levels, and the ability to transport charge and form stable molecular glasses of 4-(diphenylamino)benzaldehyde phenylhydrazones were investigated. Thermal properties, HOMO and LUMO energy levels, and

Full text of DOI:10.1007/s00706-009-0202-y

Monatsh Chem (2009) 140:1453–1458
DOI 10.1007/s00706-009-0202-y
ORIGINAL PAPER
Study on the influence of methyl groups and their location
on properties of triphenylamino-based charge transporting
hydrazones
•
Simona Urnikaite Maryte Daskeviciene
•
•
•
Tadas Malinauskas Vygintas Jankauskas
Vytautas Getautis
Received: 31 March 2009 / Accepted: 11 October 2009 / Published online: 11 November 2009
Ó Springer-Verlag 2009
Abstract Methyl substituent effects on the HOMO and
LUMO energy levels, and the ability to transport charge
and form stable molecular glasses of 4-(diphenyl-
amino)benzaldehyde phenylhydrazones were investigated.
Thermal properties, HOMO and LUMO energy levels, and
hole mobility values are dependent on the number of
methyl substituents and their position in the investigated
transporting materials. Surprisingly, however, the presence
of methyl groups at any position negatively affects the hole
drift mobility of the molecularly doped polymers contain-
ing those hydrazones.
to the evolution of xerography, charge transport materials
played a major role [2]. In recent years, several families of
hole transporting materials have been increasingly studied
[3]. High photosensitivity, good enough charge-transport-
ing properties for technical applications, simple synthesis
and low cost are the main advantages of aryl aldehyde
hydrazones compared to other classes of charge transport
materials [4]. Numerous investigations are being carried
out aimed at enhancement of hole drift mobility; however,
until now only a few concrete recommendations have been
made with regard to molecular structure modification. Only
limited data are available concerning the influence of alkyl
substituents on the qualitative parameters of charge trans-
porting layers (CTL). The importance of these groups can
be seen while constructing the frame of an effective
photoconductor using N,N,N0,N0-tetraarylbenzidine deriva-
tives [5]. In our previous paper [6] we reported on the
thermal and photophysical properties of N,N,N0,N0-tetra-
arylphenylenediamine derivatives. The introduction of
methyl groups into the N-substituted phenyl moiety in all
cases increases the photosensitivity and reduces the resid-
ual potential considerably. On the other hand, the presence
of alkyl substituents enhances the stability of the glassy
state of such p-electron-conjugated systems. In addition,
the highest mobility was observed in transporting materials
(TM) containing methyl groups at the para positions of the
side benzene rings and at the central ring of these p-elec-
tron starburst molecules [7].
Keywords Charge transport ꢀ Hydrazones ꢀ
Ionization potential ꢀ Substituent effects
Introduction
Charge transport materials are employed in various fields
such as electrophotography (photoreceptors of copying
machines, laser printers and modern fax machines), dis-
plays (organic light emitting diodes), power generation
(solar cells), memory devices (field effect transistors), etc.
The first industrial scale application of organic semicon-
ductors was xerography [1]. Of many technologies that led
S. Urnikaite ꢀ M. Daskeviciene ꢀ T. Malinauskas ꢀ
V. Getautis (&)
Department of Organic Chemistry,
Kaunas University of Technology,
_
Radvilenu˛ pl. 19, 50270 Kaunas, Lithuania
e-mail: vgetaut@ktu.lt
In this paper we present a study on the influence of
methyl groups and their location on HOMO and LUMO
energy levels, ability to transport charge and form stable
molecular glasses in hydrazones bearing a triphenylamine
moiety. The 4-(diphenylamino)benzaldehyde phenylhyd-
razones were chosen as they are among the most usable and
effective organic hole transporting materials [4]. Methyl
V. Jankauskas
Department of Solid State Electronics, Vilnius University,
_
Sauletekio 9-III, 10222 Vilnius, Lithuania
123

1454
S. Urnikaite et al.
groups were selected because of the commercial avail-
ability of the starting materials; moreover, there is a very
slight difference between methyl and ethyl groups in regard
to the charge transport ability [5].
Typical DSC analysis curves of 2 are presented in
Fig. 1. Melting temperatures, tendency to crystallize and
formation of the glassy state are noticeably influenced by
the position and amount of the methyl substituents. The
synthesized charge transporting materials exhibit
a
relatively stable glassy state; they do not undergo crystal-
lization after melting and subsequent cooling.
Results and discussion
Introduction of the methyl group at the p-phenyl posi-
tion of triphenylamine or N-phenylhydrazone fragments
results in a 9 °C decrease in melting temperature in com-
parison with 1. This slight decrease can be attributed to a
plasticizing effect of the aliphatic group. Glass transition
temperatures, however, remain almost unchanged. Methyl
groups at the o- or m-position affect the conformation of
the molecule more substantially, thus increasing the num-
ber of conformers and changing the way of packing of the
molecules. Tm of the hydrazone 3 decreases by 30 °C with
respect to unsubstituted compound 1, and 4 is already an
amorphous material. Glass transition temperatures are also
affected somewhat more substantially, i.e., Tg decreases by
ca. 3 and 11 °C for 3 and 4 accordingly. It is interesting to
note that the presence of para substituents in both tri-
phenylamine and N-phenylhydrazone fragments (6)
increases Tm by ca. 8 °C compared with 2 and 5. Most
likely the molecule of hydrazone 6 assumes a more planar
conformation, thus allowing more tight packing of the
molecules.
The synthesis of 4-(diphenylamino)benzaldehyde phen-
ylhydrazones 1–6, possessing different numbers and
positions of methyl substituents, is shown in Scheme 1.
The general synthetic procedure for all of these derivatives
involves the well-known reaction of suitable aldehydes
with the corresponding phenylhydrazines, followed by N-
alkylation reaction with iodomethane in the presence of a
base.
Formation of the glassy state was confirmed by differ-
ential scanning calorimetry (DSC) analysis. The melting
points (Tm) and glass transition temperatures (Tg) of the
investigated TMs are presented in Table 1.
H
H
N
N
O
N
R'
H2N
N
R
R'
N
R
Since p-electrons are very important for the charge
transporting process in conjugated TM structures, their
state was explored from the light absorption spectra of
hole transporting hydrazones 1–6. Comparison of elec-
tron absorption bands of 4-(diphenylamino)benzaldehyde
phenylhydrazones 1–6, possessing methyl substituents in
different locations (Fig. 2), reveals that they are similar,
except for 4-(diphenylamino)benzaldehyde N-methyl-N-
(2-methylphenyl)hydrazone (4).
CH3
N
-
CH3I, OH
N
R'
N
R
1
H
2
H
3
H
4
5
6
CH3
R
H
CH3
The latter acts somewhat unusually—the hypsochromic
shift of its extinction maximum is by ca. 14 nm in com-
parison with other hydrazone derivatives. This indicates
that the methyl group at o-position restricts p-electron
R’
H
p-CH3 m-CH3 o-CH3
H
p-CH3
Scheme 1
Table 1 Thermal, photophysical and optical properties of 1–6
Compound
Tm (°C)
Tg (°C)
Ip (eV)
(HOMO)
EA (eV)
(LUMO)
S0 - S1
(eV)
l0 (cm2 V-1 s-1
)
l (cm2 V-1 s-1
)
FL kmax (nm)a
1
2
3
4
5
6
a
153
144
123
–
35
36
32
24
35
36
5.46
5.40
5.45
5.47
5.40
5.38
2.36
2.31
2.37
2.22
2.31
2.25
3.10
3.09
3.08
3.25
3.09
3.13
4.5 9 10-6
2.0 9 10-6
2.2 9 10-6
1.5 9 10-7
3.2 9 10-6
3.0 9 10-6
1.2 9 10-4
3.8 9 10-5
4.0 9 10-5
5.0 9 10-6
6.0 9 10-5
6.0 9 10-5
422
421
423
402
419
421
144
152
kex = 360 nm (4), kex = 380 nm (for the rest)
123

Influence of methyl groups and their location on properties
1455
Cooling
36 oC
1 heating
2 heating
CH3
N
N
N
CH3
144 oC
25
50
75
100
125
150
175
200
250
300
350
400
450
500
550
600
Temperature / oC
nm
Fig. 1 DSC curves of 2 (heating rate 10 °C min-1
)
Fig. 3 Estimation of HOMO–LUMO energy band gap (S0-S1) of
compound 1 from intersection of normalized UV–Vis and fluores-
cence spectra
1
60
2
3
4
5
6
374 nm
determined from intersection of normalized UV–Vis and
fluorescence spectra (as shown in Fig. 3), and electron
affinity (LUMO) values were calculated using Eq. 1.
Estimated values are presented in Table 1.
370 nm
356 nm
50
40
30
20
10
0
LUMO ¼ Ip ꢁ ðS0 ꢁ S1Þ
ð1Þ
From the data presented in Table 1 it can be stated that
Ip of 2 and 5, possessing methyl substituents at the p-
phenyl positions of triphenylamine or N-phenylhydrazone
fragments, is lower by ca. 0.06 eV as compared to the
hydrazone 1. Addition of two methyl groups leads to a
further Ip value decrease down to 5.38 eV in the TM 6,
which means better hole injection conditions. Hydrazones
3 and 4, containing methyl groups at ortho or meta
positions, do not demonstrate such behavior, and their
ionization potentials are close to that of unsubstituted
compound 1. Furthermore, the values of ionization
potential change depend on the position of the methyl
substituents: p- \ m- \ o-. It is clear from this data that
charge carriers in p-phenyl based TMs must be excited
more easily. The LUMO levels follow pretty much the
same pattern as Ip except for ortho substituted hydrazone 4.
Its LUMO energy level is noticeably lower (2.22 eV)
compared to derivatives 1–3. Obviously, the o-substituent
significantly hinders formation of the flat stereo structure.
The magnitudes of the HOMO–LUMO gap for 1–6
correlate with the observed absorption and emission
properties. Thus, the most blue-shifted compound 4
shows the highest HOMO–LUMO gap of 3.25 eV, and
the most red-shifted 3 corresponds to a gap of 3.08 eV.
Low-molecular-weight TMs containing hydrazone
moieties are usually crystalline materials not capable of
200
250
300
350
400
450
/ nm
Fig. 2 Light absorption spectra of 1–6 in THF (c = 10-4 M)
conjugation in this molecule. Obviously, the o-substituent
hinders formation of the flat stereo structure and thus
prevents p-electrons from joining a common system. In
addition, a small bathochromic shift (4 nm) was observed
for the hydrazone 6, possessing two methyl groups in p-
phenyl positions of both triphenylamine and N-phen-
ylhydrazone fragments. This can be explained by r–p
conjugation and a consequent electron density delocaliza-
tion [5]. On the other hand, this effect was not observed in
the case of other hydrazones 2, 3 and 5.
It is known that materials used for optoelectronic devi-
ces have to meet certain HOMO and LUMO energy level
requirements; therefore, it is important to measure these
parameters. The ionization potential Ip (HOMO) was
measured by the electron photoemission in air method,
the HOMO–LUMO energy band gap (S0 - S1) was
123

1456
S. Urnikaite et al.
forming thin neat homogenous layers, and are used in
combination with polymeric hosts in a mass proportion of
1:1 [2]. The hole drift mobilities of the molecular mixtures
of the investigated hydrazones with polycarbonate-Z
(PC-Z) were estimated by xerographic time of flight
(XTOF) technique. XTOF measurements revealed that
small charge transport transients are Gaussian with well-
defined transit time on linear plots in all the investigated
samples (Fig. 4). Figure 5 shows the room temperature
dependencies of the hole drift mobility on the electric field
in hydrazones 1–6. The values of the hole drift mobility l
and l0 found by extrapolation of the experimental depen-
dencies to the values of the electric field E = 106 V cm-1
and E = 0 V cm-1 accordingly are given in Table 1.
The hole mobility is dependent on the number of methyl
substituents and their position in the TM. Higher mobility
was observed in compounds 5 and 6 containing methyl
groups at the p-phenyl position of the triphenylamine
fragment. Interestingly, however, an additional methyl
group in p-position of the hydrazone fragment (6) did not
yield further positive effects. Slightly worse results were
obtained when methyl substituents are located at the m- or
p-positions of the hydrazone fragment (2, 3). And the lowest
mobility was observed in compound 4 containing a methyl
group in the ortho position. Surprisingly, however, the best
results were observed in hydrazone 1 with no additional
methyl groups. It is obvious that the total conjugation and
HOMO, LUMO energy levels of the TM molecules are not
an obligatory precondition for a more effective charge
transport, because of other effects taking place in the charge
transporting layer. One of the reasons could be less efficient
arrangement of the molecules in the molecularly doped
polymers. This, in turn, means larger distances between
charge hopping sites and decreased mobility values.
In conclusion, we have presented a study on the influence
of methyl groups and their location on HOMO and LUMO
energy levels, the ability to transport charge and form stable
molecular glasses in hydrazones bearing a triphenylamine
moiety. The presence and position of the substituents
influence melting temperature and, to a smaller extent, glass
transition temperature. A methyl group at o-position of the
hydrazone fragment alters the conformation of the molecule
quite significantly in turn affecting thermal, optical and
photophysical properties of the compound. Substituents
located at p-position of the triphenylamine or hydrazone
fragments effectively reduce the ionization potential. Sur-
prisingly, however, the presence of methyl groups at any
position negatively affects the hole drift mobility of the
molecularly doped polymers containing those hydrazones.
1
10
t=25oC
3
+PC-Z, 1:1
U0:
0
10
880 V
684 V
544 V
428 V
304 V
222 V
146 V
92 V
-1
10
0,4
-2
10
0,2
0,0
-3
10
428 V
UV flash
0,0000
0,0002
0,0004
t / s
-6
10
-5
10
-4
10
-3
10
-2
10
t / s
Experimental
Fig. 4 XTOF transients for 3 composition with PC-Z (1:1). Insert
shows a typical transient curve in linear plot
1
The H NMR spectra were taken on a Varian Unity Inova
(300 MHz) spectrometer. Elemental analyses (C, H, N)
were conducted using the Elemental Analyser Exeter
Analytical CE-440; their results were found to be in good
agreement ( 0.2%) with the calculated values. The UV
spectra were recorded on a Spectronic Genesys 8 spec-
trometer in THF. A 10-4 M solution of the investigated
TM and a microcell with an internal width of 1 mm were
used. IR spectroscopy was performed on a Perkin Elmer
Spectrum BX II FT-IR System using KBr pellets. Fluo-
rescence emission and excitation spectra were recorded
with a Hitachi MPF-4 luminescence spectrometer. Melting
points were determined in capillary tubes using an Elec-
trothermal MEL-TEMP capillary melting point apparatus.
The course of the reactions was monitored by TLC on
ALUGRAMÒ SIL/UV254 plates and development with UV
10-3
t=25oC
10-4
10-5
1
2
3
4
5
6
10-6
10-7
0
200
400
600
E1/2 / (V/cm)1/2
800
1000
1200
˚
light. Silica gel (grade 62, 60–200 mesh, 150 A, Aldrich)
Fig. 5 The electric field dependencies of the hole drift mobility in the
CTL of hydrazones 1–6 doped in PC-Z (50 wt.%)
was used for column chromatography.
123

Influence of methyl groups and their location on properties
1457
Thermal properties for 1–6 were examined by using a
Netzsch STA 409 PC Luxx apparatus under inert atmo-
sphere. The samples were prepared by placing 5 mg of neat
hydrazone derivative into an aluminum sample pan and
crimping the upper lid to produce a hermetically sealed
sample for DSC testing. The results were normalized on a
per unit mass basis. During the first heating the melting
points were measured. After melting, the samples were
cooled with the same rate. The resulting glasses were
heated again under the same conditions to measure the
glass transition temperatures. A scan rate for all DSC
was added. The mixture was refluxed until the arylaldehyde
disappeared (TLC control). At the end of the reaction, the
mixture was cooled to room temperature. The crystals
formed upon standing were filtered off and washed with a
mixture of ethyl acetate and n-hexane (1:1) to give the
corresponding phenylhydrazone, which was subjected to
the reaction with iodomethane without further purification.
General method for the preparation of hole
transporting hydrazones 1–6
cycles was 10 °C min-1
.
Method A
Samples for the charge carrier mobility measurements
were prepared by casting the solutions of mixtures of
investigated compounds with binder material PC-Z (Iupi-
lon Z-200 from Mitsubishi Gas Chemical Co.) at a mass
proportion of 1:1 in THF. The substrate was a polyester
film with an Al layer. After coating, the samples were
heated at 80 °C for 1 h. The thickness of the CTL varied in
the range of 7–11 lm. The hole drift mobility was mea-
sured by XTOF technique [8]. Positive corona charging
created an electric field inside the TM layer. The charge
carriers were generated at the layer surface by illumination
with pulses of a nitrogen laser (pulse duration was 2 ns,
wavelength 337 nm). The layer surface potential decrease
as a result of pulse illumination was up to 1–5% of the
initial potential before illumination. The capacitance probe
that was connected to the wide frequency band electrom-
eter measured the speed of the surface potential decrease
dU/dt. The transit time tt was determined by the kink on the
curve of the dU/dt transient in linear or double logarithmic
scale. The drift mobility was calculated by the formula
l = d2/U0tt, where d is the layer thickness and U0 the
surface potential at the moment of illumination.
A mixture of the corresponding arylaldehyde phenylhyd-
razone (22 mmol), benzyltriethylammonium chloride
(2 mmol), iodomethane (132 mmol) and a catalytic amount
of potassium iodide was stirred at room temperature in
36 cm3 toluene for 0.5 h. Then aqueous 50% KOH
(154 mmol) was added, and the obtained mixture was
refluxed until the starting arylaldehyde phenylhydrazone
disappeared. After the termination of the reaction (TLC,
acetone:n-hexane = 3:22), the reaction mixture was treated
with toluene and washed with distilled H2O. The organic
layer was dried over anhydrous MgSO4 and filtered. After
removal of the solvent and excess of iodomethane, the res-
idue was dissolved in toluene and allowed to stand at 5 °C
for 12 h. The obtained crystals were filtered off and washed
with 2-propanol. Compound 3 was purified by column
chromatography (eluent: acetone: n-hexane = 2:23).
Method B
To a refluxing mixture of the corresponding arylaldehyde
phenylhydrazone (22 mmol) and 80 cm3 iodomethane 85%
powdered KOH (85 mmol) and anhydrous Na2SO4
(8 mmol) were added in three equal portions every 1 h.
After the termination of the reaction (TLC, acetone:
n-hexane = 1:4) the desired products were isolated by
column chromatography according to the procedure
described above.
Samples for the ionisation potential measurement were
prepared by dissolving the TM in THF and coating on Al
plates pre-coated with a *0.5 lm methylmethacrylate and
methacrylic acid copolymer sub-layer. The thickness of the
TM layers was 0.5–1 lm. The ionization potential Ip was
measured by the electron photoemission in air method,
similar to the one used in [9] and described in [10].
All chemicals were purchased from Aldrich and used as
received without further purification, except for 4-(N-(4-
methylphenyl)-N-phenylamino)benzaldehyde, which was
synthesized by the well-known Vilsmeier-Haack reaction
[11].
4-(Diphenylamino)benzaldehyde
N-methyl-N-phenylhydrazone (1, C26H23N3)
Synthesized according to Method A. The yield of 1 was
76%; m.p.: 156–157 °C; 1H NMR (300 MHz, CDCl3):
d = 7.65 (d, J = 8.7 Hz, 2H, p-subst. Ph of triphenyl-
amine), 7.54 (s, 1H, CH=N), 7.47–7.29 (m, 8H, Ar), 7.23–
7.07 (m, 8H, Ar), 6.98 (t, J = 7.0 Hz, 1H, 4-H Ph), 3.47 (s,
3H, CH3) ppm; IR (KBr): vꢀ ¼ 3; 057; 3,023 (CHar), 2,930,
2,899, 2,813 (CHal), 827, 756, 748, 727, 701, 696, 688
General method for the preparation of arylaldehyde
phenylhydrazones
(CH=CH of mono- and 1,4-disubst. benzene) cm-1
.
4-(Diphenylamino)benzaldehyde
To arylaldehyde (22 mmol) dissolved in 25 cm3 toluene the
corresponding arylhydrazine (26 mmol) or arylhydrazine
hydrochloride (53 mmol) dissolved in 50 cm3 methanol
N-methyl-N-(4-methylphenyl)hydrazone (2, C27H25N3)
Synthesized according to Method A. The yield of 2 was
70%; m.p.: 147–149 °C; 1H NMR (300 MHz, CDCl3):
123

1458
S. Urnikaite et al.
d = 7.64 (d, J = 8.7 Hz, 2H, p-subst. Ph of triphenyl-
amine), 7.50 (s, 1H, CH=N), 7.39–7.04 (m, 16H, Ar), 3.44
(s, 3H, N-CH3), 2.37 (s, 3H, CH3) ppm; IR (KBr): vꢀ ¼
3; 084; 3,058, 3,032 (CHar), 2,934, 2,902, 2,854, 2,813
(CHal), 839, 833, 812, 752, 737, 694 (CH=CH of mono-
4-(N-(4-Methylphenyl)-N-phenylamino)benzaldehyde
N-methyl-N-(4-methylphenyl)hydrazone (6, C28H27N3)
Synthesized according to Method B. The yield of 6 was
75%; m.p.: 155–157 °C; 1H NMR (300 MHz, CDCl3):
d = 7.54 (d, J = 8.7 Hz, 2H, p-subst. Ph of triphenyl-
amine), 7.40 (s, 1H, CH=N), 7.31–7.17 (m, 4H, Ar), 7.15–
6.93 (m, 11H, Ar), 3.34 (s, 3H, N–CH3), 2.31 (s, 3H, CH3),
2.28 (s, 3H, CH3) ppm; IR (KBr): vꢀ ¼ 3; 061; 3,024 (CHar),
2,915, 2,856, 2,810 (CHal), 817, 797, 756, 732, 714, 696,
and 1,4-disubst. benzene) cm-1
.
4-(Diphenylamino)benzaldehyde
N-methyl-N-(3-methylphenyl)hydrazone (3, C27H25N3)
Synthesized according to Method A. The yield of 3 was
59%; m.p.: 124–126 °C; 1H NMR (300 MHz, CDCl3):
d = 7.55 (d, J = 8.6 Hz, 2H, p-subst. Ph of triphenyl-
amine), 7.42 (s, 1H, CH=N), 7.27–6.92 (m, 15H, Ar), 6.73–
6.69 (m, 1H, Ar), 3.35 (s, 3H, N–CH3), 2.33 (s, 3H, CH3)
ppm; IR (KBr): vꢀ ¼ 3; 086; 3,062, 3,033 (CHar), 2,993,
2,896, 2,811 (CHal), 768, 748, 729, 694 (CH=CH of mono-
678 (CH=CH mono- and 1,4-disubst. benzene) cm-1
.
Acknowledgments We are grateful to Habil. Dr. V. Gaidelis for the
help in ionization potential measurements. Financial support of this
research by the Lithuanian Science and Studies Foundation is grate-
fully acknowledged.
and 1,4-disubst. benzene) cm-1
.
References
4-(Diphenylamino)benzaldehyde
1. Grazulevicius JV, Strohriegl P (2001) Charge-transporting poly-
mers and molecular glasses. In: Nalwa HS (ed) Handbook of
advanced electronic and photonic materials and devices, vol 10.
Academic Press, San Diego, pp 233–274
2. Borsenberger PM, Weiss DS (1993) Organic photoreceptors for
imaging systems. Marcel Dekker, New York, p 447
3. Shirota Y (2000) J Mater Chem 10:1
4. Lygaitis R, Getautis V, Grazulevicius JV (2008) Chem Soc Rev
37:770
5. Nubada K, Sata K, Akasaki Y (1991) Electrophotography 30:16
N-methyl-N-(2-methylphenyl)hydrazone (4, C27H25N3)
Synthesized according to Method B. The yield of 4 was
43%; 1H NMR (300 MHz, CDCl3): d = 7.46 (d,
J = 8.6 Hz, 2H, p-subst. Ph of triphenylamine), 7.33–
6.93 (m, 17H, Ar, CH=N), 3.29 (s, 3H, N-CH3), 2.32 (s,
3H, CH3) ppm; IR (KBr): vꢀ ¼ 3; 058; 3,023 (CHar), 2,924,
2,860 (CHal), 825, 753, 722, 694 (CH=CH mono- and 1,2-,
1,4-disubst. benzene) cm-1
.
ˇ
_
6. Getautis V, Stanisauskaite A, Paliulis O, Uss S, Uss V (2000)
4-(N-(4-Methylphenyl)-N-phenylamino)benzaldehyde
N-methyl-N-phenylhydrazone (5, C27H25N3)
J Prakt Chem 342:58
7. Getautis V, Paliulis O, Gaidelis V, Jankauskas V, Sidaravicius J
(2002) Photochem Photobiol A 151:39
8. Montrimas E, Gaidelis V, Pazera A (1966) Lithuanian J Phys
6:659
9. Miyamoto E, Yamaguchi Y, Yokohama M (1989) Electropho-
tography 28:364
10. Daskeviciene M, Getautis V, Grazulevicius JV, Stanisauskaite A,
Antulis A, Gaidelis V, Jankauskas V, Sidaravicius J (2002)
J Imaging Sci Technol 46:467
ˇ
Synthesized according to Method B. The yield of 5 was
79%; m.p.: 144–146 °C; 1H NMR (300 MHz, CDCl3):
d = 7.54 (d, J = 8.7 Hz, 2H, p-subst. Ph of triphenyl-
amine), 7.45 (s, 1H, CH=N), 7.38–7.18 (m, 6H, Ar), 7.18–
6.94 (m, 9H, Ar), 6.88 (t, J = 7.0 Hz, 1H, 4-H Ph), 3.37
(s, 3H, N-CH3), 2.31 (s, 3H, CH3) ppm; IR (KBr): vꢀ ¼
3; 061; 3,024 (CHar), 2,921, 2,902, 2,813 (CHal), 827, 820,
727, 716, 698, 689 (CH=CH mono- and 1,4-disubst.
11. Vilsmeier V, Haack A (1927) Chem Ber 60:119
benzene) cm-1
.
123